Fire alarm device



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D 3 R 3 m. Z 6 m 0 0 Z Jan. 15, 1957 w. c. MESSICK FIRE ALARM DEVICEFiled Nov. 13, 1955 fl K flTTorPA/svs Jan. 15, 1957 w. c. MESSICK FIREALARM DEVICE 2 Sheets-Sheet 2 Filed NOV. 13, 1955 INVENTOR WILLARD C.MESSICK HTTOPNYS United States Patent FIRE ALARM DEVICE Willard C.Messick, Summit, N. J., assignor to Fyr-Larm Co., Inc., Summit, N. J., acorporation of New Jersey Application November 13, 1953, Serial No.391,848

7 Claims. (Cl. 116-106) The present invention relates to a signallingdevice and relates, more particularly, to a fire alarm device which willautomatically produce an audible signal when the temperature of theatmosphere surrounding the device is raised by a fire or similar hazard.

An object of the invention is to provide a fire alarm device which isentirely self-contained and which will produce an audible signal for aconsiderable period of time when the ambient temperature is raised to apredetermined temperature. Another object of the present invention is toprovide a fire alarm device which is reliable in its operation and whichmay be produced at a relatively low cost. Other objects and advantagesof the invention will be apparent and best understood from the followingdescription and the accompanying drawings in which:

Fig. l is a front view of a fire alarm device embodying the presentinvention;

Fig. 2 is a fragmentary section view taken along the line 2-2 of Fig. 1;

Fig. 3 is an end view of a part of the fire alarm device illustrated inFig. 1;

Fig. 4 is a section view taken along the line 44 of Fig. 3;

Fig. 5 is an end view of another part of the fire alarm device shown inFig. 1 I

Fig. 6 is a side view of the part shown in Fig. 5; and

Fig. 7 is a fragmentary view in section illustrating a modification in afire alarm device embodying the invention.

Referring to the drawings in detail, there is a pressurized cylinder 10.The cylinder 10 is preferably charged with substance that will create asubstantial pressure within the container under the temperatureconditions in which the device is to operate. An example of such asubstance is a group of halogenated hydrocarbons containing one or morefluorine atoms which are known commercially as Freon and in particulardichlorodifluoromethane (CClzFz) or Freon 12 which has a boiling pointat one atmosphere of pressure of 29.8 C. or 2l.6 F. I

The Freons are especially suitable for this purpose since they arestable, non-toxic, non-flammable and noncorrosive. The use of suchsubstances also permits the cylinder to be made with relatively thinside Walls.

Satisfactory operation of a fire alarm embodying the invention has beenobtained by charging a cylinder of approximately 2 inches in diameterand 11 inches in length with about ten ounces of Freon 12. Such a chargewill develop approximately 80 lbs. per square inch pressure withinthecylinder at 78 F. and approximately 200 lbs. per square inch pressureat 136 F. The vapor pressure Within the cylinder may be developed withdifferent amounts of Freon, but the duration of the audible signal willdepend on the amount of Freon in the cylinder.

iThe top of the cylinder 10 has a threaded opening 11 Z ,7 7'7 ,4 l 6Patented Jan. 15, 1957 'ice The temperature head 12 is an elongated bodyhaving an enlarged portion and which is formed of metal havingrelatively high thermal conductivity such as brass. The temperature headextends beyond the top of the cylinder and its outer end is threaded toreceive a sound producing unit indicated generally at 14.

As shown best in Figs. 3 and 4, the temperature head has a passageway 15therein 'which communicates at one end with the interior of the cylinderand at the other end with an orifice 16. To prevent foreign bodies inthe cylinder from entering the passageway 15, a screen 17 may be placedover the end of the passageway communicating with the cylinder.

The orifice 16 communicates with an expansion chamber 18 in thetemperature head through an outlet 19 and the expansion chamber 18 inthe temperature head communicates with the sound producing unit. Thus,the orifice 16 controls the rate at which the vapor under pressure inthe cylinder can escape through the temperature head to the soundproducing unit. In the device illustrated and described herein, anorifice of about twenty eight thousandths of an inch (.0028) in diameteris provided in the temperature head.

The orifice 16 and the outlet 19 are closed by a fusible metal plug 20which will melt or fuse when the temperature head is heated to aselected temperature. An eutectic metal which will melt at 136 F. ispreferably used for this purpose, however, other'suitable metal having aknown melting point may be used. When the temperature of the plug 20 israised to a point where the fusible metal starts to melt, such meltingwill first take place along the sides of the plug which are in contactwith the temperature head and hence receive the heat first. When thishappens, the sides of the plug melt, the bond between the plug and thetemperature head is broken and the plug will be blown out of the orificeand the outlet by the pressure within the cylinder.

The bottom of the expansion chamber 18 slopes downwardly away from theoutlet 19 to form a groove 18a surrounding the outlet. This prevents thepossibility of the plug 20 falling back into the outlet and causingintermittent operation of the signalling device after the plug has beenblown out of the outlet and since there will be no pressure beneath theplug, it will remain in the groove.

It is important to secure a leak-proof permanent bond (up to 136 F.)between the fusible metal plug and the temperature head and to minimizeplastic flow of the fusible metal of the plug. This may be accomplishedby use of a flux which will cause an interfacial migration be tween thetin in the fusible metal and the metal of the temperature head. Thisremoves the possibility of the pressure within the cylinder forcing anuncontrolled opening along the side of the fusible plug. The bottom ofthe outlet 19 may also be sloped downwardly, as indicated at 19a, so asto increase the area of the plug that is in contact with the temperaturehead. This also tends to increase the resistance of the plug to beingblown out of the outlet prematurely and prevents leaks from developing.

The orifice 16 also reduces the effective area of the plug on which thepressure in the cylinder is exerted and thus, aids in preventing theplug from being blown out of the outlet and orifice at temperaturesbelow that at which the device is to operate.

For the purpose of conducting heat from the surrounding atmosphere tothe temperature head, a heat conducting hood 21 is secured to thetemperaturehead at a point adjacent the outlet and orifice. The hood 21is made of corrugated metal and is insulated from the sound producingunit by a fibre washer 21a to prevent the bleeding of heat away from thetemperature head. The hood directs upwardly rising heated air toward thetemperature head and has vents 22 therein which permit the flow of theheated atmosphere through the hood and provide for a more efiectivetransfer of heat to the temperature head. In addition, the temperaturehead has a portion of reduced area, as indicated at 23, to provide for amore rapid and efiective heat transfer to the fusible plug 20.

The sound producing unit 14 which is secured to the outer end of thetemperature head, consists of a T-shaped fitting 24. As shown in Fig. 2,the leg of the T-shaped fitting is threaded to the outer end of thetemperature head and communicates with and forms a continuation of theexpansion chamber 18 in the temperature head. A perforated disc 25 islocated between the fitting and the end of the temperature head toprevent the plug or other foreign bodies from entering the soundproducing unit.

The top of the T-shaped fitting forms a sound chamber 26 which is openat both ends. A vibratable reed 27 is located in one end of the chamber26 and a relief valve 28 is located in the other end of the chamber. Thereed 27 is mounted on a reed plate 29 which seats against a shoulder inone of the openings in the fitting. The reed plate 29 is held in placeby a horn 30 which is threaded into the opening in the fitting. Theouter end of the born 30 is covered by a protective screen 31.

The relief valve 28 normally closes the other opening to the chamber 26,but will open automatically when the pressure in the chamber exceeds aselected pressure. The relief valve 28 includes a sleeve 32 which isfitted in the opening in thefitting and has an inwardly extending flange32 at its inner end forming a valve seat. A semispherical valve member34 is held in engagement with the flange 32 by a spring 35. The spring35 is held in engagement with the valve member by a perforated springretaining cup 36 which is forced into the opening in the end of thefitting.

When the pressure exerted against the valve member from within thefitting exceeds a pressure of approximately two pounds per square inch,the valve member will be forced away from the valve seat against theaction of the spring. This relieves the pressure acting on the reed 27and prevents the reed from becoming blocked and being renderedinoperative as may happen when a vibratable reed is subjected toexcessive pressures such as may develop during the initial surge ofvapor pressure escaping from the cylinder. It will be understood howeverthat the reed will blow while the relief valve is open under suchconditions.

A modified form of relief valve is illustrated in Fig. 7. hi this form,there is a reed 27' which is mounted on a reed plate 29'. The reed plate29' is movably mounted inside of the end of a horn 30' which is attachedto a fitting 24 and is held against the end of the fitting by a spring37. The other end of the spring 37 engages with an indentation 358 inthe born. The reed plate is slightly smaller in diameter than theinterior of the horn and when the reed plate is moved away from thefitting against the pressure of the spring, the pressure inside thefitting will be relieved by the passage of the vapor past the edges ofthe reed plate. In this construction, the other end of the chamber inthe fitting will be closed.

As shown in Fig. 7, the end of the horn of the sound producing unit maybe sealed by a thin disc 39 of metal to prevent atmospheric conditionsfrom affecting the reed. The disc 39 is of a slightly convex shape andmay be held in place by a ring 40 of fusible metal which will melt andrelease the disc at or before the time that the fusible plug intemperature head has been blown out of the orifice. This also provides aconvenient way of determining if thedeviceis in operating condition. Ifthe device has operated when no one is present, the disc will have beenremoved from the horn and this can then be determined by a visualinspection of the unit.

The operation of the signalling device will now be described. When thetemperature of the atmosphere surrounding the device is raised to aselected temperature such as 136 F. which would indicate the pressure ofa fire, the heat is conducted to the temperature head by the heatconducting hood. The temperature head due to its thermal characteristicswill-be heated by the increase in temperature and will conduct the heatto the fusible plug closing the orifice and the outlet therein. The heattransmitted to the fusible plug will cause the sides of the plug to meltand the plug will be blown from the orifice and outlet in thetemperature head by the pressure within the cylinder. It will beunderstood that the pressure within the cylinder will also increase withthe increase in temperature.

When the outlet and orifice in the temperature head are opened in thismanner, the vapor within the cylinder escapes through the orifice andoutlet to the expansion chamber at a rate controlled by the orifice. Inthe expansion chamber, the vapor expands and its pressure is reducedbefore it passes through the fitting to the reed chamber. From the reedchamber, the vapor passes through the reed and thus, produces an audiblesignal. If the pressure of the vapor in the reed chamber exceeds thepressure at which the reed will operate, the relief valve automaticallyopens until the pressure of the vapor in the reed chamber is reduced toa suitable value.

It has been found by actual tests with signalling devices embodying thepresent invention, that the plug of fusible metal will be releasedcleanly and quickly from the outlet and orifice in the temperature headwhen the ambient temperature reaches 136 F. and that an audible signalof over decibels will be produced continuously for a prolonged period soas to give an ample warning of a fire or similar hazard. Depending onthe temperature reached, the signal will continue from five to twelveminutes.

It will be understood that various modifications may be made by thoseskilled in the art in the embodiments of the invention illustrated anddescribed herein without departing from the scope of the invention asdefined by the following claims.

I claim:

1. In a self-contained, temperature sensitive signalling device of thetype having a cylinder containing a supply of vaporizable fiuid underpressure such as dichlorodifluoromethane therein, the improvement whichcomprises a fitting of heat conducting material located in an opening inthe top of a cylinder, said fitting having a passageway extendingtherethrough and communicating with the interior of the cylinder, anannular shoulder in said passageway forming a restricted orifice thereinat a point intermediate its ends, and a plug of fusible material closingone end of said passageway, said plug being located in the passageway onthe side of the orifice away from the interior of the cylinder and beingin contact with the annular shoulder forming said orifice and with thesides of said passageway.

2. In a self-contained, temperature sensitive signalling device, theimprovement as defined in claim 1 wherein the fitting of heat conductingmaterial has an enlarged body portion located on the exterior of thecylinder and a heat conducting hood is secured to said body portion incontact therewith, said hood extending outwardly be yond the enlargedbody portion of said fitting and having a number of perforations thereinfor permitting the flow of air through said hood and around the enlargedbody portion of the fitting.

3. In a self-contained, temperature sensitive signalling device, theimprovement as defined in claim 1 which includes a second 'fittinghaving imperforate side walls secured to the fitting of heat conductingmaterial, said second fitting having an expansion chamber thereincommunicating with the passageway in the fitting of heat conductingmaterial and a discharge outlet communicating with the chamber, and avibratable reed mounted in said discharge outlet whereby an audiblesound will be produced by the passage of vapor under pressure from theexpansion chamber through said discharge outlet.

4. In a self-contained, temperature sensitive signalling device, theimprovement as defined in claim 1 which includes a second fitting havingimperforate side walls secured to the fitting of heat conductingmaterial, said second fitting having an expansion chamber thereincommunicating with the passageway in the fitting of heat conductingmaterial and a discharge outlet communicating with said chamber, avibratable reed mounted in said discharge outlet whereby an audiblesound will be produced by the passage of vapor under pressure from theexpansion chamber through said discharge outlet, and valve means forrelieving the pressure of the vapor in the expansion chamber and actingon said vibratable reed.

5. In a self-contained, temperature sensitive signalling device, theimprovement as defined in claim 1 which includes a second fitting havingimperforate side walls secured to the fitting of heat conductingmaterial, said second fitting having an expansion chamber thereincommunicating with the passageway in the fitting of heat conductingmaterial and a discharge outlet communicating with said chamber, avibratable reed mounted in said discharge outlet whereby an audiblesound will be produced by the passage of vapor under pressure from theexpansion chamber through said discharge outlet, valve means forrelieving the pressure of the vapor in the expansion chamber and actingon said vibratable reed, said valve means including a tubular valve bodyfitted into an opening in the second fitting and communicating with theexpansion chamber, said valve body having an inwardly extending annularflange forming a valve seat at one end thereof, a valve member movablymounted in said valve body, and a spring engaging with said valve memberand normally holding said valve member in engagement with the valve seatagainst the pressure of the vapor in the expansion chamber.

6. In a self-contained, temperature sensitive signalling device, theimprovement as defined in claim 1 wherein the fitting of heat conductingmaterial comprises an elongated body having an enlarged portion locatedon the exterior of the cylinder and includes a heat conducting hoodsecured to said body in contact therewith, said hood extending beyondsaid body and having perforations therein for the passage of air throughthe hood, a second fitting secured to the fitting of heat conductingmaterial, said second fitting having an expansion chamber thereincommunicating with the end of the first fitting containing the fusibleplug and a member of insulating material interposed between the hood andthe second fitting.

7. In a self-contained, temperature sensitive signalling device, theimprovement as defined in claim 1 which includes a second fitting havingimperforate side walls secured to the fitting of heat conductingmaterial, said second fitting having an expansion chamber thereincommunicating with the passageway in the fitting of heat con ductingmaterial and a discharge outlet communicating with the chamber, and avibratable reed mounted in said discharge outlet whereby an audiblesound will be produced by the passage of vapor under pressure from theexpansion chamber through said discharge outlet, a heat conducting hoodsecured to said first fitting and contacting therewith, said hoodextending beyond said fitting and having perforations therein for thepassage of air through said hood and a member of insulating materialinterposed between the hood and second fitting.

References Cited in the file of this patent UNITED STATES PATENTS999,567 Kallstrom Aug. 1, 1911 1,540,023 Kollinek June 2, 1925 1,926,688Schaal Sept. 12, 1933 2,034,179 Franklin Mar. 17, 1936 2,177,594 EavesOct. 24, 1939 2,211,142 Loudon Aug. 13, 1940 2,483,657 Messick Oct. 4,1949 2,649,752 Showstack Aug. 25, 1953 FOREIGN PATENTS 517,072 FranceApr. 29, 1921

